Diffusion-weighted MRI of the breast: its role in clinical practice

Author: Dr Sarah J Vinnicombe

Excerpt: 

Breast MRI is the most sensitive imaging test available for breast cancer detection. The fundamental breast MRI sequence is dynamic contrast-enhanced MRI (DCE-MRI), with repeated acquisition of T1-weighted (T1w) gradient echo sequences through both breasts before and after intravenous injection of gadolinium-based contrast agents. It depicts the vascularity of tissues and the morphological and kinetic information provided yields sensitivities for malignancy of over 90%, particularly for invasive breast cancers. However, not all benign and malignant lesions can be differentiated with DCE-MRI alone and there are persistent concerns over the relatively large number of false positive examinations. The addition of diffusion-weighted imaging (DWI) to DCE-MRI can significantly increase the specificity of the examination without loss of sensitivity. DWI probes the motion of water molecules in biological tissues, which is influenced by underlying tissue microstructure, viscosity, cellularity and cellular membrane integrity, rather than simple lesion vascularity. It has the great advantage of being quantifiable through measurement of the apparent diffusion coefficient (ADC) and it does not require intravenous contrast. Together, DCE, DWI and morphological sequences such as high resolution T2-weighted sequences constitute multiparametric breast MRI (mpMRI), which yields multifaceted, nuanced information on tumour biology. This article considers the basic principles of DWI, interpretation, current utility and research avenues.

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